1. Field
The present disclosure relates to lignin microcapsules and a method for preparing the same. More particularly, the present disclosure relates to lignin microcapsules having a micro/nano-structure and a method for preparing the same.
2. Description of the Related Art
Lignin is a natural polymeric compound and a fat-soluble phenol polymer present at the cell walls of lignified plants, such as conifers or broad-leaved trees. Lignin is not amenable to acid hydrolysis due to its characteristic amorphous structure and has a chemical structure in which constitutional units of C3-C6 phenylpropane groups are condensed through carbon-carbon or ether bonds. Recently, importance of a biomass as a raw material for bioenergy has been increased, and thus many studies have been conducted about controlling the lignin content in a biomass by introducing the characteristics of enzymes involved in biosynthesis of lignin and molecular biological technologies, fibrillation of lignin, and about encapsulation of lignin.
A self-healing or self-restoring system refers to a system designed to have properties with which some defects can be detected and restored spontaneously according to specific environments such as heat, electricity and light with no artificial operation. Among such systems, applications of a self-healing material using microcapsules have been suggested in Nature, 2001 by the professor White in University of Illinois—Urbana-Champaign (UIUC) (USA). Particularly, microcapsules are added to a polymer matrix, external force is applied to the polymer matrix so that the polymer matrix is damaged, the wall materials of capsules are broken around the damaged portion, and then the internal core materials (curing agent or matrix reinforcing material, or the like) are discharged so that the polymer matrix restores its original physical properties.
Carbon nanotubes have a graphene layer wound in a cylindrical shape. Carbon nanotubes have been given many attentions as a first-dimension nanomaterial applicable to various industrial fields by virtue of their electrical and mechanical properties. However, there are many limitations in applying carbon nanotubes due to strong cohesive force unique to nanomaterials. To solve such a problem, a non-covalent functionalization method using various types of dispersants, polymers, DNA, proteins, or the like has been suggested. Particularly, there have been conducted studies about stabilization and efficient control of the dispersive property of carbon nanotubes in the presence of a solvent by using lignin.